1. Field of the Invention
The invention in general relates to the analysis of an unknown gas, and more particularly to a solid state miniature mass spectrometer.
2. Description of Related Art
A mass spectrometer is a device that permits rapid analysis of an unknown gas sample. A small amount of the gas to be analyzed is introduced into the mass spectrometer where it is ionized, focused and accelerated, by means of magnetic and/or electric fields toward a detector array. Different ionized gas constituents travel along different paths to the detector array in accordance with their mass to charge ratios. The outputs from the individual detector elements of the array will then provide an indication of the gas constituents.
Industrial mass spectrometers are generally large, heavy and expensive. Therefore a need exists for a miniature, relatively inexpensive light-weight solid state mass spectrometer for use by the military, homeland security, hazmet crews and industrial concerns, by way of example.
One such miniature solid state mass spectrometer is a MEMS (microelectromechanical system) device described in U.S. Pat. No. 5,386,115. Basically, the described device is comprised of two semiconductor substrates joined together by an epoxy seal. Each half includes intricate cavities formed by a lithographic process. Although the device meets the requirement for small size, due to the depth and intricacy of the cavities, the lithographic process is extremely expensive. Further, under vacuum conditions, the epoxy seal may tend to outgas into the device thus contaminating the readings obtained and limiting its sensitivity.
Accordingly, the mass spectrometer of the present invention is a MEMS device which obviates the drawbacks of the prior art.